Both the paper & ROS Form 11 for 2008 contain the following statement:
"If you wish to elect under Section 305(1)(b) TCA 1997 to set any unused Capital Allowances (not already ring-fenced) in respect of Buildings for 2008 against your other income state the amount of unused Capital Allowances available for offset below:"
PS - Items in Bold are "Bolded" by Revenue, not me.
So, unless you are willing to take Revenue to court in an attempt to argue your interpretation of Sect 305, I would be inclined NOT to try to claim excess capital allowances against other income.